Faecal indicator bacteria and toxic metal concentrations in domestic and irrigation water from main gardening sites in Kinshasa, Democratic Republic of the Congo

In Sub-Saharan African countries, urban market gardening plays a significant socio-economic role in enhancing food security, combating hunger, supporting daily livelihoods, and reducing unemployment. Fresh vegetable gardening is widely practiced in urban and peri‑urban communities, employing thousands of people and providing over 70 % of the fresh vegetables consumed in cities. Many urban and peri‑urban families live near or on these production sites and use water from springs, shallow wells, and untreated contaminated river water for irrigation and domestic use. Consequently, monitoring and assessing the water quality is key to preventing potential health risks, not only for users, but also for irrigated vegetables; when consumed raw, they are at risk of becoming contaminated with pathogens. In this study, water samples were collected from two major market gardening sites in Kinshasa-Lutendele and Cecomaf-and analyzed for microbiological and physicochemical parameters. The microbiological assessment focused on faecal indicator bacteria (FIB), including Escherichia coli (E. coli), Enterococcus (ENT) and total coliforms (TC). The physicochemical analysis includes parameters such as pH, electrical conductivity (EC), dissolved oxygen (O₂), dissolved organic carbon (DOC), total organic carbon (TOC), major soluble ions (Na^+, K^+, NH₄⁺, PO₄³, SO₄^2-, NO₃^-, and NO₂^-), and metals and metalloids (Cu, Zn, Cr, Ni, Co, Ag, Cd, Sb, Pb, As, Se, Fe, Mn, V and Ti) . Microbiological analysis of water samples from all sites showed elevated levels of FIB, reaching concentrations of 5.5 × 10³, 1.9 × 10⁴ and 2.2 × 10⁴ CFU 100 mL^-1 for E. coli, ENT and TC, respectively. Concentrations of soluble ions such as PO₄^3-, NO₃^-, NH₄⁺, and K⁺ were 2 to 10 times above the acceptable limits according to the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) guidelines for irrigation and domestic use. Despite this, almost all metal concentrations remained below FAO and WHO guidelines. However, given the above acceptable limits of FIB and soluble ions detected in irrigation water, the use of such water may pose potential health risks through direct consumption, contamination of raw vegetables, or dermal contact during irrigation.